Pole-piece for dynamo-electric machines.



No. 676,439. Patented-lune l8, I90I.

.F. A. MERRICK. POLE PIECE FOR DYNAHO ELECTRIC MACHINES.

(Appli on filed Mar. 20, 1901 I IIIIIIIIIIIIIIIIIIII I III'III III IIIIIIIIIIIIIIIIIIIII f ZIIIIUI II II III III I v llll I "II IIIIII II II I I I II I II II II II III II II II II II II III II I|II| III] II III I I I IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII |||||||I I||IIII||||II||||||I|IIIIIIIIIIIIIIIIIIII I i 4 struction in which counterpartlaminae-musti l ,FRANKJA. MERRIOK,OF JoHNsT owN, PENNSYLVANIA,."AssIeNoR To rHE.

It i lE- mmm i i i s emi ers retentive.s'za ieaaaeanae 1's,19o1. 1

' To allwhomjit mag concern;

, LORAIN, fsT L. COMPANY, OF. PENNSYLVANIA,

Po repee Fo'R DvN Moe ELECTRIC 'M c Hi 4 ESQ f by f uBe itkn'ow-n that I, FRANK A. MERRIGK, of;

Johnstowmin' the county ofCambria and StateofPennsylvania, have invented a new [and useful Improvement in Pole-Pieces for,

Dynamo-Electric Machines,of which thefollowing is a full, clear,-an'd exact description,

tion.

I f 'M invention.has'relationto theconstruc-' "tion' of pole-pieces, for dynamo-electric mai fchines, and'is designed-to provide ineansfor preventing"orreducingdistortion or the mag netic'field due to cross magnetization of-the rotating armature. Y

.For well -known reasonsfpole s pieces" are i usually of laminated construction, audit has I been common prior to my invention to counteract the distorting effe'ct'of cross magnetiz'ation by so shapingand,assembling'the lami nee-that the polar edges of alternate lamina:

, a or portions thereof extend nearer the periphcry of the armature than'the corresponding portions of adjacent laminae, thus reducing theamountofmetalat the polar tacev of the,

" piec'e'or-at the tips thereof,-tothereby produce magnetic saturation or supersaturation I of the metal to; sucha degree that further passage of magnetic linesof force-through those portions-of the poles is. checked, This requires either theuse of two difierent forms of lamina? placed alternately with respect to each other or" else the alternate assembling-of counterpart laminae; The first-named cons struction 'isobjectionable'in that two different diesmust beemployed in the production 7 of the laminae, and care must be taken in assembling, and this last-mentioned objection applies with still greater forceto the con- 7 "be assembled in alternate relation.

'that the end portions of each are also counterparts of each other, so that they may be assembled without regard to end relation.

My invention is also distinguished from the prior art above referred to in that instead of utilizingthel magnetic resistance of saturated metal "to counteract-the distorting effect of armature cross-magnetization I utilize the re-;

sistance of, a'sornewhateincreased airgap between the tip fportions of the poles'andt-he periphery of tlie armature, and thus tend to pr'e'ventsaturationat'snch points. i Specifically'considered, my'invention consists in a plate or lamina for pole pieces having aconcaved inner or polar'edge bounded by a compound curve whosecent-ral portion is concentric with the axis, of the armature andwhoseend portions are each of a greater radius.

In the accompanying drawings, Figure 1 is a plan view of one of my improved laminae; Fig. 2, a similarview showing 'how the lamina is cut away to receive the heads of the bolts -which secure the pole-piece to its seat',and Fig. 3 is a plan view'of a completed pole-,

piece. v

Referring more specifically to Fig. 1, the

centralportion of the concaved edge of the lamina from the point l'to the point 2-has a radius of curvature concentricwith the armaturea xis,.while the curvature of the end por-.

tions 1 3 ison a slightly-greater radius, the

radii of both such portions being from a common' center. The intersection of the curves 1 3 with the'curve'l 2is at the points 1 and 2, as shown. Theextent to which the radii of curvaturejof the end portions 1 3 are increased'will depend somewhat upon the par ticular character of the machine, but is pref= erablyfrom one-eighth to three-sixteenths of an inchl The effect of this increase in radius is, as indicated by thedotted line in r Fig. 1, to gradually increase the width of the air-gap between the armature and the polepiece from the points 1 and 2 outwardly to.

In constructing apole-piece from these I 

